Flops for complete intersection Calabi-Yau threefolds

We study flops of Calabi-Yau threefolds realised as Kähler-favourable complete intersections in products projective spaces (CICYs) and identify two different types. The existence the type can be recognised from configuration matrix CICY, which also allows for constructing such examples. first corresponds to rows containing only 1s 0s, while second a single entry 2, followed by 0s. give explicit descriptions manifolds obtained after flop show that always leads isomorphic manifolds, general non-isomorphic flops. singular involved are determinantal varieties case more complicated case. discuss admitting an infinite chain how these matrix. Finally, we point out construct divisor images Picard group isomorphisms under both types